1. Field of the Invention
The present invention relates to the structure of a switch used as a power switch used in, for example, a washing machine, a dish washer, or a drying machine, and more particularly to the structure of a push-button switch incorporating a self-restoring function.
2. Description of the Related Art
FIGS. 11 to 14 illustrate the structure of a conventional push-button switch incorporating a self-restoring function. More specifically, FIG. 11 is a partly cutaway plan view showing a state in which the push-button switch is locked. FIG. 12 illustrates the relationship between a lock cam and a lock pin of FIG. 11. FIG. 13 is a partly cutaway plan view showing a state in which a solenoid of the push-button switch is performing an actuating operation. FIG. 14 illustrates the relationship between the lock cam and the lock pin of FIG. 13.
In these figures, a frame member 11 is formed by pressing a metallic plate, such as a steel plate. An AC switch section 12 and a solenoid 13 are integrally mounted side-by-side to the frame member 11. A DC switch section 14 is mounted behind the AC switch section 12.
A sliding member 15 is slidably disposed on the AC switch section 12. By pushing in the sliding member 15, a circuit provided at the AC switch section 12 and a circuit provided in the DC switch section 14 are turned on. The sliding member 15 is biased towards an initial position thereof by a restoring spring (not shown). When the sliding member 15 is in the initial position, the circuits of the AC switch section 12 and DC switch section 14 are turned off.
A heart cam 16 is disposed at the sliding member 15, and includes a protrusion-like lock cam 16a at the center portion thereof. A lock pin 17 (described later) is made to slide along the lock cam 16a. By stopping the lock pin 17 by a surface of the lock cam 16a, the sliding member 15 is locked in a pushed-in state.
The lock pin 17 is formed by bending both ends of a round rod at right angles, with a lock-pin fulcrum 17a being formed at one end thereof and a lock-pin operating end 17b being formed at the other end thereof. The lock-pin fulcrum 17a is axially supported in a hole (not shown) formed in the frame member 11, while the lock-pin operating end 17b, which is rotatable, is disposed so as to slide along the lock cam 16a of the heart cam 16.
An actuating cam 18 includes a cam protrusion 18a at the center portion thereof. The cam protrusion 18a is rotatably axially supported by the frame member 11. One end of the actuating cam 18 is engaged and connected to an iron core 13a of the solenoid 13. The actuating cam 18 is formed so that it can be rotationally driven around the cam protrusion 18a as a fulcrum by the force of attraction of the solenoid 13. On the other hand, the other end of the actuating cam 18 is disposed near the heart cam 16 disposed at the sliding member 15, with inclined surfaces 18b and 18c together forming a triangular shape at the tip of this other end of the actuating cam 18. The actuating cam 18 is disposed between the AC switch section 12 and the frame member 11.
The operation of the conventional push-button switch incorporating a self-restoring function will be described. When the sliding member 15 is pushed in, it is kept in a pushed-in position. In this pushed-in position, the operating end 17b of the lock pin 17 is stopped by the lock cam 16a, so that the sliding member 15 is locked in the pushed-in position. From this pushed-in position, when the solenoid 13 is energized by a signal transmitted from an external control circuit (not shown), the force of attraction of the solenoid 13 causes the actuating cam 18 to rotate around the cam protrusion 18a as the fulcrum by the iron core 13a. At this time, the inclined surface 18b formed at the end of the actuating cam 18 which has rotated comes into contact with the operating end 17b from a longitudinal direction of the lock pin 17 (or a direction perpendicular to the direction of movement of the lock pin 17). and guides and moves the operating end 17b in a horizontal direction (or a downward direction in the figures). This causes the operating end 17b to disengage from a stopper section of the lock cam 16a of the heart cam 16, so that the sliding member 15 is unlocked.
However, in the structure of the conventional push-button switch incorporating a self-restoring function, when the sliding member 15 is in the locked state, the operating end 17b of the lock pin 17 is held by the stopper section of the lock cam 16a, whereas, when the sliding member 15 is in an auto-off state, the operating end 17b of the lock pin 17 is disengaged from the lock cam 16a as a result of pushing the operating end 17b of the lock pin 17 horizontally by the inclined surface 18b at the end of the actuating cam 18 actuated by the solenoid 13. Therefore, friction between the lock pin 17 and the lock cam 16a is large, so that a large force is required to unlock the lock pin 17. This results in the problem that the amount of actuating current supplied to the solenoid 13 becomes large.
In addition, since the lock pin 17 is forced to disengage from the stopper section of the lock cam 16a by pushing the lock pin 17 horizontally, the lock pin 17 is severely worn, which may prevent a highly reliable product with a long life from being manufactured.
Further, the actuating cam 18 actuated by the solenoid 13 is rotated to unlock the lock pin 17, so that the actuating cam 18 is increased in size, thus making it difficult to reduce the size of the product.